1. Field of the Invention
The present invention relates to infrared sensors and methods for manufacturing infrared sensors. In particular, the present invention relates to infrared sensors including optical filters disposed in openings of packages that accommodate infrared sensor elements, the optical filters functioning to deliver infrared rays having a predetermined wavelength to the infrared sensor elements and define lids to seal the openings of the packages, and to methods for manufacturing the infrared sensors.
2. Description of the Related Art
As shown in FIG. 5, a known optical semiconductor device 51 includes a base (package) 54 having a recessed portion 54a provided in the top surface thereof, an optical semiconductor element 52 disposed on the bottom surface of the recessed portion 54a, and a tabular light transmitting cover (optical filter) 53 attached to the top surface of the base 54 surrounding the recessed portion 54a via an ultraviolet curable resin 55 (see Japanese Unexamined Patent Application Publication No. 2003-163297).
In the optical semiconductor device 51, a main surface of the light transmitting cover 53 adjacent to the recessed portion 54a is coated with an optical thin film 53a to block light beams in a predetermined wavelength band, and a portion of the optical thin film 53a in an area 53b in which the light transmitting cover 53 is bonded to the top surface of the base (package) 54 surrounding the recessed portion 54a is mechanically removed so that the bonding strength between the light transmitting cover 53 defining an optical filter and the base 54 is improved. This optical semiconductor device including the light transmitting cover 53 is capable of being produced at low cost and is compact and highly reliable.
However, the optical semiconductor device 51 described in Japanese Unexamined Patent Application Publication No. 2003-163297, in which the optical thin film 53a of the light transmitting cover (optical filter) 53 at a bonding surface to be bonded to the base (package) 54 is removed and the light transmitting cover (optical filter) 53 is bonded to the base (package) 54 at the bonding surface as described above, has the following problems.
Since the optical filter, which is expensive, is bonded to the package at the outer periphery of the light receiving surface of the optical filter, the optical filter does not function at the outer periphery, resulting in an increase in cost.
The amount of adhesive applied or the state of the applied adhesive may vary, and adhesion failure or oozing of the adhesive to portions other than the bonding portion may result. When such an optical semiconductor device is applied to an infrared sensor used for, for example, detection of human bodies and security equipment, the detection range may be reduced, and the field-of-view characteristics may vary.
In order to obtain a sufficient bonding strength during bonding, it is necessary to chemically or mechanically remove the optical thin film at the bonding portion. This complicates the manufacturing processes and increases the cost thereof.